The most general phrases that seems appropriate to start the discussion would be soundboard (de- and re-)compression over both bridges, and the string segmentation tension differentials. Seems enough. :-) ? Cheers, ? Paul Paul When?I first started tuning 32 years ago,?my?dad told me?that the reason a piano goes flat after a pitch raise is because strings have memory and want to "go back where they came from".?Then I learned that the reason a piano goes flat after a pitch raise is because the soundboard compresses. Then someone told me that the bridge rolls during a pitch raise. But my question are, how much memory does a string have, how long does it take for the soundboard to compress, and when does the bridge stop rolling? I have done some research on this, and my contention is that?old?strings do not have memory, (a new one?stretches, but not because of memory),?the soundboard?stops compressing and the bridge stops rolling as soon as the?strings have been?pulled up to pitch.?After that, it's just matter of stabilizing the tuning, just as you would during a "normal" tuning. Is this the physics you're talking about? Have you done research on this? Have you taken an badly out of tune piano, lets say 50 cents low, and done a pitch raise and fine tuning in one setting, then checked it a day later, a week later, a month later? Providing the environment in which the piano is sitting is stable, what kind of results did you get? I ddi this about 10 years ago, and tracked my results, which showed the pitch didn't alter.?And I just did this?on a 50 year old Everret Studio?sitting in my office. When it came in two weeks ago, it was 45 cents flat. I?pitch raised?and fine tuned it.?I just now played it, and it's a little sour,?but then it's sitting in front of an open window and partly opened patio door.?But in general it sounds pretty good. ? Wim -----Original Message----- From: PAULREVENKOJONES at aol.com To: pianotech at ptg.org Sent: Fri, Aug 28, 2009 2:01 pm Subject: Re: [pianotech] PR follow up ? In a message dated 8/28/2009 6:36:33 P.M. Central Daylight Time, davidlovepianos at comcast.net writes: Please explain the physics as you know it that would account for this. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20090828/bcf64d63/attachment.htm>
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